0fe765a977
add support for 32k XTAL as RTC_SLOW_CLK source - RTC_CNTL_SLOWCLK_FREQ define is removed; rtc_clk_slow_freq_get_hz function can be used instead to get an approximate RTC_SLOW_CLK frequency - Clock calibration is performed at startup. The value is saved and used for timekeeping and when entering deep sleep. - When using the 32k XTAL, startup code will wait for the oscillator to start up. This can be possibly optimized by starting a separate task to wait for oscillator startup, and performing clock switch in that task. - Fix a bug that 32k XTAL would be disabled in rtc_clk_init. - Fix a rounding error in rtc_clk_cal, which caused systematic frequency error. - Fix an overflow bug which caused rtc_clk_cal to timeout early if the slow_clk_cycles argument would exceed certain value - Improve 32k XTAL oscillator startup time by introducing bootstrapping code, which uses internal pullup/pulldown resistors on 32K_N/32K_P pins to set better initial conditions for the oscillator. Ref TW11683. Ref https://esp32.com/viewtopic.php?f=13&t=1570 Fixes https://github.com/espressif/esp-idf/issues/337. See merge request !696 |
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